At the small local clinic near her home in Sabana Grande, Puerto Rico, doctors ran a battery of tests on Cuascud before sending her by ambulance to a larger regional hospital where she was poked and prodded some more, she said. No one stopped to explain anything to her and she said she said she remembers feeling scared, alone and confused.

Doctors were confounded as to why Cuascud was hitting puberty so early. Besides breast growth, she had also sprouted pubic and underarm hair and went through a sudden, dramatic growth spurt. They were even more puzzled, she recalled, when she began menstruating shortly before she turned 7.

Puberty Comes Earlier

The average of age of puberty has been getting steadily lower since the early 20th century, when girls had their first period at age 16 or 17, according to the American Academy of Pediatrics. Now the average age for a first period is closer to 12, with one University of Cincinnati study reporting that about 10 to 15 percent of girls enter puberty at age 7 or younger, a phenomenon known as precocious puberty. This is up from just 5 percent in similar studies conducted in the early 1990s.

Many experts speculate puberty is starting younger because of better health and nutrition. Others blame chemicals that mimic hormones in the environment or meat injected with growth hormone. Still others point to the rise in childhood obesity. So far, evidence for any one theory remains both elusive and inconclusive.

For example, early studies associated an increase in body mass index with elevated blood levels of estrogen, a hormone that causes breast development and sexual development. However, more recent studies found that in general, children are going through puberty earlier regardless of their weight.

The Dangers of Early Puberty

Even with girls maturing 4 or 5 months sooner each decade, Dr. Angela Diaz, a pediatrician at Mt. Sinai Medical Center in New York City, said that cases like Cuascud’s where development occurs before the age of 8 aren’t the norm.

“It’s true that I am seeing girls in my practice mature younger than ever before but when they mature before the age of 10, there is often something wrong,” Diaz said.

Precocious puberty can be caused by a tumor or a malfunction of the pituitary gland, an organ that, among other things, secretes and stores sexual hormones, Diaz said. It’s important to be seen by an endocrinologist for diagnosis and treatment, she said, because early maturity can lead to problems later in life.

“Despite any early growth, some girls don’t continue to grow and mature normally,” she said. “Some studies have also shown that girls who start puberty very young are more likely to develop breast and uterine cancer later in life.”

And in addition to the physical health implications, Diaz said she there could also be psychological ramifications.